Tissues deprived of blood and oxygen undergo ischemic necrosis or infarction with possible irreversible organ damage. Cerebral ischemia results from decreased blood and oxygen flow implicating one or more of the blood vessels of the brain. In cerebral ischemia, the individual suffers a stroke with sudden development of a focal neurologic deficit and, in most cases, some degree of brain damage. The decreased blood flow may be due to, for example, an occlusion such as a thrombus or embolus, vessel rupture, sudden fall in blood pressure, change in the vessel lumen diameter due to atherosclerosis, trauma, aneurysm, developmental malformation, altered permeability of the vessel wall or increased viscosity or other quality of the blood. Decreased blood flow may also be due to failure of the systemic circulation and severe prolonged hypotension. Ischemic necrosis of the spinal cord may result in sensory or motor symptoms or both that can be referred to cervical, thoracic or lumbar levels of the spine. Ischemic heart disease results from an imbalance between myocardial oxygen supply and demand. In ischemic heart disease, the individual suffers angina pectoris, acute myocardial infarction or sudden death. The imbalance may be caused by, for example, atherosclerotic obstruction of one or more large coronary arteries, nonatheromatous coronary obstructive lesions such as embolism, coronary ostial stenosis associated with luetic aortitis, coronary artery spasm, congenital abnormalities of the coronary circulation, increased myocardial oxygen demands exceeding the normal supply capabilities as in severe myocardial hypertrophy, reduction in the oxygen carrying capacity of the blood such as n anemia, or as a consequence of inadequate cardiac perfusion pressure due to hypotension from any cause. U.S. Pat. No. 6,294,579 B1 discloses methods for treating ischemia by administering certain Deltorphin peptides. The publication by Lazarus et al., “Environmental Health Perspectives”, Vol. 102, No. 4, pages 648-654 (1994), discloses naturally occurring opiod peptides.
Current treatments for ischemia encompass behavioral changes drug therapy, and/or surgical intervention. Drugs are frequently preferred before resorting to invasive procedures and to provide more immediate relief than long-term behavioral changes. Thus, there is a need for a therapeutic agent which can be useful in treating or preventing ischemia.